------- Comment #2 from rguenth at gcc dot gnu dot org 2010-06-29 12:07 -------
Note that the issue is that PRE pessimizes code by transforming
if (D.3841_10 != 0)
goto <bb 4>;
else
goto <bb 7>;
<bb 7>:
goto <bb 5>;
<bb 4>:
pos_11 = i_24 + 1;
<bb 5>:
# pos_1 = PHI <pos_23(7), pos_11(4)>
# limit_4 = PHI <limit_25(7), limit_9(4)>
i_13 = i_24 + 1;
to
if (D.3841_10 != 0)
goto <bb 4>;
else
goto <bb 7>;
<bb 7>:
pretmp.4_22 = i_24 + 1;
goto <bb 5>;
<bb 4>:
pos_11 = i_24 + 1;
<bb 5>:
# pos_1 = PHI <pos_23(7), pos_11(4)>
# limit_4 = PHI <limit_25(7), limit_9(4)>
# prephitmp.5_21 = PHI <pretmp.4_22(7), pos_11(4)>
i_13 = prephitmp.5_21;
which exposes the fact that we do not do code-hoisting presently.
Removing the IV restriction from PRE would create i_24 + 1
as new IV with an increment in the latch block.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2010-06-29 12:07:13
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44711
